1. Field of the Invention
The present general inventive concept relates to an image forming apparatus to control noise, and more particularly, to a method of controlling noise generated by an image forming apparatus in a standby mode.
2. Description of the Related Art
Image forming apparatuses (for example, printers) include an exposure unit performing an exposure process with respect to a photosensitive drum according to printing data that is to be printed and forming an electrostatic latent image, a developing unit developing the electrostatic latent image using developer, a transfer unit transferring the developed image onto a printing medium, a fusing unit to fuse the transferred image to the printing medium, and a switch mode power supply (SMPS) converting alternating power supplied from outside of the image forming apparatus into direct power of a predetermined voltage to supply the power at a predetermined operating frequency. A typical image forming apparatus also includes a filter to filter noise in the image forming apparatus, and a controller controlling operations of the exposure unit, the developing unit, the transfer unit, the fusing unit, and the SMPS.
The operating frequency of the SMPS may vary depending on the power supplying load of the SMPS. However, since the load of the SMPS for applying the power is quite high when the image forming apparatus is in a standby mode (for example, the SMPS only supplies the power to the controller when the image forming apparatus is in the standby mode), the SMPS operates at a certain operating frequency when the image forming apparatus is in the standby mode. Subsequently, noise is generated at the certain operating frequency and a multiplying frequency of the operating frequency. Accordingly, it is difficult to control the noise generated in the standby mode in the conventional image forming apparatus.
Additionally, the fusing unit is a fusing roller including a heating resistance member that generates heat in response to the power supplied from outside of the image forming apparatus. In order for the fusing unit to perform the fusing operation, a temperature of a surface of the fusing roller should reach a predetermined value. Regarding the conventional image forming apparatus, power is sometimes supplied to the heating resistance member in the standby mode so that the surface temperature of the fusing roller can be maintained at a certain temperature value in order to print the printing data as fast as possible. However, since the temperature of the heating resistance member in the standby mode is low, much over-current flows to the heating resistance member and the filter cannot perform properly when the power is supplied to the heating resistance member in the standby mode of the image forming apparatus. Accordingly, it is difficult to control noise, particularly when power starts to be supplied to the fusing unit while the image forming apparatus is in the standby mode.